If you can build a space elevator then you've just removed any need to use Mars or anywhere else other than Earth as a base for exploration/exploitation. With the massive cost of lifting materials to orbit reduced it makes sense to build things where you have food, water, air, radiation shielding and all that other good stuff. Using the Moon or Mars as a base only makes sense if the costs of contending with gravity are more than the costs of building and sustaining a base on another celestial body.
Presuming there's still benefit, as far as can be seen now there's nothing going for Mars as a base for exploiting the resources of the solar system compared to the Moon. The moon is closer and much easier to get to and has lower gravity than Mars which makes landing and launching less expensive. Both have few resources and we don't yet know whether there is water that can be exploited in either location, or how we would use it.
The solar system subway map is a great way to illustrate why Mars doesn't make a great base for exploring/exploiting compared to the moon as it shows the delta-V you need for each leg of a journey from one body to another.
Getting from the surface to the Earth to LEO is 9400m/s, then escaping Earth's gravity takes an additional 3210m/s, from there to get to another body takes whatever delta-v it says to its intercept. So to get from the surface of the Earth to escape velocity is 12610m/s. For Mars it is 5240 and for the Moon a mere 2410m/s. To get from Moon intercept or Earth intercept to other objects takes the same delta-v, and I'm going to assume 2600m/s from Moon/Earth intercept to the asteroid belt as it's half-way between Mars and Jupiter (an oversimplification but it works in this case). Using that figure it's 5010m/s to get from surface of the Moon to the asteroid belt, From Mars I'm going to assume 1300m/s delta-v from Mars intercept to the asteroid belt, so it would be 6540m/s.
So looking at the delta-v figures it's cheaper to launch from the Moon. It's also much, much easier and cheaper to get equipment, supplies and personnel to the Moon.
In many ways Mars really only makes sense from a redundancy perspective, a self-sustaining colony on Mars would save the human race from extinction in the case of a cataclysm on Earth.